Scott's campaign pleaded for "emergency" donations because Nelson must not be allowed "to derail a conservative nominee."

Nelson's campaign warned donors that if Scott wins in November, "Republicans will keep their grip on the Senate – and we'll have no chance to stop any extreme nominees."

President Donald Trump plans to nominate Kennedy's successor July 9. And Senate Majority Leader Mitch McConnell, R-Ky., is insisting the Senate confirm the nominee this fall, a move analysts say could occur well before the Nov. 6 election.

Sen. Bill Nelson, D-Fla.(Photo: Manuel Balce Ceneta, AP)

Even so, the vacancy is expected to ratchet up the tension and importance of a nationally watched race that could decide who controls the Senate next year and, in turn, the confirmation of future nominees to federal courts. Republicans hold a 51-49 margin in the Senate.

Incendiary issues such as immigration, gun control and abortion already are convincing donors to dig deeper into their pockets and pushing more people to political activism. But the prospect of a Supreme Court vacancy will spike turnout even more in the fall elections, said Susan MacManus, a retired political science professor at the University of South Florida in Tampa.

"The courts do get both sides of the aisle charged up," she said, especially in a mid-term congressional election such as this year's "when the predominance of turnout is activists and longtime party members."

The just-completed term has reminded voters of the court's importance as the ultimate referees on some of the most polarizing issues dividing Americans.

Supreme Court Justice Anthony Kennedy(Photo: Manuel Balce Ceneta/AP)

From President Trump's immigration travel ban to workers' rights, voting rights and religious rights, the nation's highest court handed conservatives a nearly unbroken string of victories in rulings that were often 5-4 with Kennedy as the swing vote on the prevailing side.

How the vacancy will play in swing elections like the Florida Senate race will largely depend on whom Trump selects when he unveils the pick July 9, MacManus said.

Trump said he will pick from a list of 25 potential nominees assembled previously with the help of conservative interest groups. If he chooses a woman, a minority or a relatively moderate jurist, it could put Democrats in closely contested races such as Nelson in a tougher bind to go against them, MacManus said.

On the other hand, a recent poll suggests Nelson might benefit from Kennedy's retirement.

Nearly 50 percent said they are voting for more Democrats "to be a check and balance" on Trump compared with 40 percent who say their vote "will send a message that more Republicans are needed to help Trump pass his administration’s agenda," according to the NBC News/Marist poll.

The survey of 1,083 Florida adults, conducted just before Kennedy announced his departure, has a margin of error of plus or minus 3.7 percentage points.

Nelson wants the confirmation process to take place after the election.

"I believe the American people should be given the opportunity to express their view in the upcoming election, and then have the Senate exercise its constitutional duties," he said in a statement following the announcement of Kennedy's retirement Wednesday.

During the last Supreme Court vacancy in 2016, Nelson wanted the Senate to move on Obama nominee Merrick Garland before the election. McConnell held it up, Trump became president and conservative Neil Gorsuch was confirmed.

Already, One Nation, a conservative group, is running digital ads in Florida urging Nelson to "say 'no' to the far left" and support Trump's as-yet unnamed nominee.

"This is merely the first step in our full-fledged advocacy campaign for the nomination and confirmation of a constitutional conservative to the U.S. Supreme Court," said One Nation president Steven Law.

Scott is urging the Senate follow McConnell's lead and move quickly on the confirmation of a new justice even though it would mean he wouldn't get a chance to vote on the choice.

"We cannot delay having a solid justice and Senate Democrats should not try to play politics or obstruct this process," Scott said. "It's imperative the next justice will uphold our Constitution and fairly and accurately interpret our laws."